The development of the industry of TFT LCDs (Thin Film Transistor Liquid Crystal Displays) and intensified competition thereof render maximization of glass utilization effective for improving product competitiveness. In order to improve glass utilization, a mask plate should be designed adjacent to edges of the glass as much as possible.
A positioning graphic component (such as a cross), as an auxiliary process structure arranged on a glass substrate, is usually placed on an outermost side of the glass substrate. FIG. 1 shows a glass substrate having four crosses respectively provided on the four corners thereof Positioning graphic components are substantially used for aligning various detection devices with the glass substrate in the processes of detecting defects, measuring sizes, film thickness, and line width, testing electric performance, and cell and assembling, etc.
Positioning graphic components in the prior art generally have a monolayer metal structure, which will be explained by taking a cross as an example. As indicated in FIG. 2, the cross is patterned during formation of a first layer of metal film in manufacturing an array substrate. An silicon nitride insulating material 22 is deposited on the patterned cross 20 via the chemical vapor deposition, wherein the silicon nitride insulating material 22 is capable of protecting the cross 20 from being etched in a subsequent etching step.
In actual manufacture of the positioning graphic component, however, the following problems might arise. Due to the restriction of chemical vapor deposition devices themselves, it is impossible for a filming area obtained from the devices to cover the edges of a glass entirely, which causes a portion of the positioning graphic component that has not been covered by the insulating film to be etched in subsequent procedures. Thus, the positioning graphic component may be incomplete.
FIG. 3(a) illustrates the positioning graphic component 20 patterned during formation of the first layer of metal film; FIG. 3(b) shows deposition, on the positioning graphic component 20, of the silicon nitride insulating material 22, which, however only covers a right portion of the positioning graphic component 20; and FIG. 3(c) shows the positioning graphic component after etching, from which it can be clearly seen that a left portion of the positioning graphic component without the protection of the insulating material is etched.
In lack of a complete positioning graphic component that can be used by a detection device, the glass substrate would be processed as waste, thus causing unnecessary losses in the production.
As a result, due to the above problems existing in the prior art, it is in urgent need in the process of manufacturing TFT LCDs to find an effective solution for preventing an incomplete positioning graphic component.